Some conventional actuators include an elongated housing, an elongated positioning element, and a motor. The elongated housing attaches to a fixed body, and the elongated positioning element attaches to an object. The motor moves the elongated positioning element along a central axis defined by the elongated housing to move the object relative to the fixed body.
To sense position, these actuators may further include a helix-shaped rotational member and a bearing element. The helix-shaped rotational member is disposed along the central axis defined by the elongated housing. Additionally, the bearing element provides support for the elongated positioning element, and enables the elongated positioning element to travel laterally along the helix-shaped rotational member and rotate the helix-shaped rotational member about the central axis in the process. As the helix-shaped rotational member rotates in response to lateral movement of the elongated positioning member, magnets mounted to the helix-shaped rotational member move past Hall sensors which detect rotation of the helix-shaped rotational member. As a result, linear movement of the elongated positioning element can be measured based on rotation of the helix-shaped rotational member.